Thunderhawk Blue vs Silver Grey

How close are they?

ΔE 15.4, loose: different enough that you should pick on purpose. Silver Grey is noticeably lighter, more muted, cooler than Thunderhawk Blue.

Can I use Silver Grey instead of Thunderhawk Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Silver Grey is noticeably lighter, more muted, cooler than Thunderhawk Blue.

Can I use Thunderhawk Blue instead of Silver Grey?

The same difference applies the other way round: Thunderhawk Blue is noticeably darker, more saturated, warmer.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.